CRX Millennium

iTrader: (1)

Since I took the ownership of my "Renesis" (as registered & licensed in NJ) in early summer '04, the experience has been mixed though enjoyable overall:

PROS:
1. Uniqueness: Nothing quite like it on the road (not as prevalent as G35 or 350Z)
2. Smoothness: Revs like a dream everytime
3. Quietness: Not Lexus-quiet but surprisingly well-managed NVH control
4. Finesse: German marque-like built that is solid and pleasing to eyes and touch

CONS:
1. Gasoline Consumption
Although not unexpected as I researched the numerous threads on the subject prior to the purchase, 16mpg(avg 15-18) is understandably disappointing for a modern-engineered car with such an efficient powerplant (HP/L-wise)

2. Fit & Finish
While the brake squeal has been mitigated somewhat by brake pad change as covered under TSB, the steering column and instrument cluster rattle annoyingly & embarrassingly upon traversing rough pavement now the car is well broken-in. The driver door panel also seems to suffer from rattle-issue.

3. Oversteer
While my RWD experience has been fairly limited to just Lexus GS300 & BMW 323Ci on a temporary basis, the RX8 lately has been a handful and sometimes hairy experience especially in dealing with the heavy & frequent raining condition in NJ this year. As covered in https://www.rx8club.com/showthread.php?t=30777, the car performed "adequately" when Pirelli PZero Nero M+S 245/40/18 tires were new. Nowadays, I had the rear-end getting loose and stepping out of trajectory path in gradual turns and ramps that has to be recovered thru counter-steering (already way too many times than I like). I reckon that driving habit can be a potential cause, though my previous driving experience under similar road condition & speed in other drivetrain configurations (FWD: CRX & Passat, RWD: GS300 & 323) had all been much "sure-footed". The tires now are about 6K miles worn and 36psi front 34psi rear. They have been through two autox events and I suspect that the heat issue might have contributed to the deteriorating handling of theses highly regarded all-season tires in wet.

Please kindly vote on the poll I have incorporated to survey owners' experience regarding RX8 and oversteer issue.

JMD RX-8

Are you mounting the 245s on the stock rims? My first thought is that you are putting a tire which is 20mm wider than OEM on the OEM wheel, and on a car which is dialed in for 225s. I can promise you at the very least this will impact your steering.

Moreover, in the thread you mentioned, CRX Millennium specifically mentions the Pirellis are a handful in the rain. I've heard this same comment from others regarding significant traction loss in the rain. If you want good rain and dry traction, go with GoodYear F1s, and stick with 225s!

CRX Millennium

iTrader: (1)

JMD RX-8,

Nice to meet a fellow Fighting Illini on the board driving the same car. Going back to the discussion, the stock size is 225/45/18. I am using 245/40/18 as based on the online tire size calculator to minimize the speedometer variance. Tire change may be in order to ensure safe driving, though the relevancy of extra 20mm should not be the overwhelming factor.

shaolin

Whenever it rains the DSC takes care of me just fine...

G8rboy

5 years with a tail-happy Miata prepared me for the RX8... I would much rather have controllable oversteer than understeer.

zevans

This car is amazingly neutral in setup. Therefore, it oversteers under big power and it oversteers under braking / lift-off.

Wider tyres will always be worse in the wet.

When things do step out in the rain the DSC gives you plenty of warning. I'm sure you could still 360 it but only if you tried.

My stock Bridgestones got noticably worse at about 5000 miles and they're now worse again after a track day. Plenty of tread left though, and "worse" just brings it down to the level of anything else I've driven.

Also, oversteer is more scary than understeer, and most cars just understeer in the rain. So some of this is because when you do lose traction it feels more worrying.

TRZ750

Anyone that is not use to a flat turning rear wheel drive car will have trouble when it gets slippery. When the first 1979 RX7s came out it was one of the first low cost cars that didn't have much body roll (compared to those days, not today as it rolls a lot compared to todays cars). When it rained MANY 7's ended up crashing. The problem was that the drivers got use to truning at a high rate as with the low body roll they felt comfortable. Then when it rained they didn't think to pay attention and ended up going too fast and loosing the car.

The RX8 has low profile tires that also you need to get use to as there is a lot less side wall flex so the tires tend to have a more sudden transision to the slide. Also less tire squell.
Anyone that has driven a rear wheel drive car very hard should understand the term "Throttle Steer". With a car with slight over steer you can use the throttle to control your turn and help square off turns.

Now with my 8 and with my older gen 1 RX7 I love the comute to work when it rains. There is a ~110 degree turn at a stop sign. I will commonly only trun the steering wheel a small amount and then pop the throttle to bring the rear around.

You need to remember the low profile tires, excellent dry handling, and quick throttle respone whenever it gets slippery. As it will be much easier to get in trouble. Find a open area like a empty parking lot on the weekend and practice turning and sliding. Or better yet attend a driving school to learn how to drive fast in both wet and ry conditions.

Gord96BRG

2 comments - One, wider tires will hydroplane more easily than narrower tires - you installed wider tires than OEM on your relatively lightweight RX-8. Wet grip WILL suffer simply from that. Two, how's your alignment? The RX-8 has a fully adjustable front and rear suspension setup, and it is entirely possible that your alignment includes insufficient rear camber or neutral toe or rear toe-out, which would definitely contribute to oversteering tendencies in the wet.

Regards,
Gordon

ivyrose

I have just about 6K miles as well and have just recently noticed the rattling issue in the driver door panel and in the instrument panel. Have you brought your 8 in for service to check this out?

Spin9k

I'm sure you realize that you have made a decision with the tire pressures to 1) have built in oversteer due to higher front pressure, and 2) by raising the pressure above the recommneded 32psi, cause the car to be more 'twitchy' than it otherwise would be.

Combining those two factors could enhance any other effects you are getting from that particular brand/size of non-OEM tire.

Why not go back to recommended pressures (32 frnt/rear) at least and see the result, if any?

LeeP

I have begun having seriously uncharacteristic oversteer on DRY PAVEMENT after having my tires rotated during the course of a 5000 mile oil change and service. Again this is on DRY pavement with factory installed tires and factory tire pressure! I am not new to rear wheel drive cars...this is a drastic change in performance of either vehicle or tires! Here are the details:

I have run this car numerous times through Deals Gap, aka The Dragon, as I live about 30 minutes from the start of it. I have made somewhere in the neighborhood of 8 to 10 hard runs of the 318 curves during my total 6100 miles in the 8. Each time the handling was smooth, precise and predictable.

It was not until I had the tires rotated that I began to notice the rear end, mainly when turning right, would rapidly jump out at speeds of no more than 35 mph under moderate throttle. Curves I could hit at 50 - 60mph now make my heart race at 40mph. This new behavior stands out so much that if I had not owned an 8 prior to this I would never buy one. If I can't find the problem I will dump the 8 asap it is so bad. It is so pronounced I can only compare it to driving on ice or snow. Either something in the suspension is loose or these tires have serious issues after being pushed hard. I seriously think tire hardening might be an issue but a visit to my local tire guy only yielded a "well I have gotten any info on these tires yet" and did say at least 70 to 80 percent of the tread was still there.

I finally got the dealership to agree to take a look and find the problem this coming Friday. If they find anything I will certainly post. Anyone else that has noticed this problem after 5500 to 6000 miles please post and share as I really want my 8 handling like it used to and would like to know if anyone else has had this problem.

Spin9k

If it started when the tires were rotated... why would you "get rid of" the 8 to solve the problem? ... rather than "get rid of" the tires? Or simply re-rotate them and see if it goes away?

Or maybe I mis-understood. Don't you like the 8? You seem to say you do?

PS at my 5k rotate the tire became terribly annoyingly noisy... but at 10K they got rotated back, and it all went away, happily.

G8rboy

Unless you've seen a considerable drop in temperatures (which I have up here in Chitown, and have noticed reduced grip and more oversteer tendancy), I would be suspect of your alignment. I screwed around with some fairly agressive alignments on my Miata and had some pretty touchy settings for a while... tail would just snap around with little warning. I also think that the Potenzas start losing their grip long before the tread goes.

LeeP

I was simply saying that IF I CAN'T FIND THE PROBLEM I WILL GET RID OF IT. I was trying to give an idea of how bad it has become after 5500-6000 miles. I am hoping it is nothing more than tires, though 5000 miles on a set is pretty bad. Even with all the Dragon runs I wasn't out sliding it through parking lots or anything.

I had strange problems early on with loose bolts on strut towers and such and was convinced this new problem was the car until I read that others are having similar problems after 5000 miles on their factory tires. Perhaps it is just a tire issue. I haven't read any research on the Bridgestones and have never had this problem with other tires. Believe me I love the 8 when all is well and am crossing my fingers that the tires are the issue.

A local RX8club member and ex-autocrosser suggested rotating the tires back to see if anything changes as the tires now on the back would have been up front and would have gotten hotter. If the compound hardens after getting very hot or being pushed hard, rotating them back might solve the problem for now. If not I will buy new tires and see what that does. I just want to make sure this isn't another loose suspension issue.

LeeP

Yeah G8rboy the alignment is another possibility. I am taking it in Friday to see if anythign is loose again or if it is alignment. If it is none of those issues one can only assume it is the tires. I instantly thought tires because that was the only change. There would be no reason to mess with the alignment during the rotation but anything is possible. And yes I LOVE THIS CAR, just not like it is handling now. Oh yeah and Gators?..ugh.

Vaillant

I agree with #2, but not #1. With higher pressure in the front tires, that should create more understeer, not oversteer. The harder the setup (tires, antiroll bars, shocks, springs) the more that side of the car will want to slide first. If this was a dry weather situation, I'd say lower the rears another 2 psi, but, in the wet, I'm not sure what that does for dealing with standing water.

~ Matt

GeorgeH

iTrader: (2)

While autocrossing on street tires, I have found that lower pressures offer more grip in inclement (cold & wet) weather. So I agree - drop your pressures to 32 all around, and have the alignment checked.

I don't find the RX-8 any more prone to oversteer than my Miata, with the exception of power-induced oversteer, of course. That's just a fact of life as you move up the power/weight scale. I have, however, found the RX-8 to be more easily catchable than the Miata.

The RX-8 is intended to be a playful car that you can adjust with the throttle. This means it probably will be a bit twitchier in the wet than a heavier luxury car, even when setup properly.

Spin9k

Well, I still think you are incorrect. Here's why and you could (VERY CAREFULLY) try this to prove it out. Let air from the rears bringing the pressure to say 24lbs, leaving 34lbs in the front. Now CAREFULLY!!, take the car out and I'm pretty sure the 1st corner you take at almost any reasonable speed, you will find the tail out all over the place. Personally, rather than do the aformentioned, I'd just believe me, so follow this - another logical explaination....

The tires need sufficiently high pressure to get a correct contact patch, and low profile tires need even more pressure than higher profile tires due to their low sidewalls in order to support the weight of the car. In our 8, 32 lbs is recommended as a balance between comfort, handling, and safety, and does support the load of the weight of the car..... but increasing the pressure (to a point) will also increase, not decrease the grip. At some higher point, the center of the tire starts to raise above the edges and grip (and contact area) will begin to decrease again, but 34/36lbs is below that point - so as grip increases as in this case on the front, so will oversteer.

Wet throws yet another variable in the mix, but the logic should stay roughly the same. Hope that helps.

Vaillant

I guess we'll just have to disagree, then.

Typically, lower pressure (to a point) increases the grip. Sure, go too far (and I think 24 psi is too far) and you'll be back to no grip. However, there's a reason drag racers lower the pressure in their driven tires...more grip! You do lose out on transient response, but you increase the grip.

After a dozen or so days on various race tracks in my Miata (we're lucky here in Nor Cal to have a bunch that are close to us) playing around with different tires and pressures, I've found that I like to run a little more pressure in the front. A little understeer is comfortable (I'm not trying to win a prize) and I like the increased responsiveness up front.

~ Matt

(I'll try to find a source for this...I've got most of the "XXXX to Win" books at home, and I'm sure it is in there somewhere. Of course, for race cars, sometimes mechanical grip suffers to increase the aerodynamic grip.)

G8rboy

That's been my experience with autocrossing- reduce pressure in the fronts to reduce understeer, and reduce pressure in the back to reduce oversteer... to a point. Of course I usually start out on the high side (36-38 psi) and back off each from there.

Spin9k

Vaillant, check this out. It's kinda long, but does cover the subject. Maybe were just disagreeing on semantics, and agreeing on what we are speaking of.

http://www.nastyz28.com/pthandle.html (skip down to "Performance Handling (Road Racing)", past the drag racing part)

or http://racerhelp.com/article_racing-9.html (same thing)

It covers air pressure as a tuning method and says what I intended to communicate, just with a lot more detail.

A quote:

"To reduce understeer you add oversteer to the car by:

* Increasing front tire and wheel size
* stiffen the rear springs
* increase front tire pressure.
* increase rear stabilizer bar."

Here's another article:

http://www.sentra.net/tech/garage/suspension.php (nice chart little way down)

GeorgeH

iTrader: (2)

So, in summary, for any given set of conditions (surface quality, temp, moisture presence) there is a "sweet spot" that offers best steady-state grip in a corner. In my experience, colder, wetter conditions have a lower pressure sweet spot. Think about it - lower temps and wet conditions mean less grip. Less grip means less sidewall distortion at the limit. Less sidewall distortion means less pressure required to maintain carcase shape. So drop the pressure to get more tire on the road.

But yes, if you go below the sweet spot (like the 24 psi condition) you will lower grip just as readily as if you over-inflate the tires. And I think drag-racing is a special situation (as is autocross). The orginal poster was talking about the rear tires loosing grip mid-turn, which is different than straight-line traction of drag racing or the transient requirements of autocross.

Vaillant

I guess, ultimately what is not known is what the highest grip pressure for our tires. I know at the track either a the tire temperature is taken or, for those of us without the laser pyrometers (or whatever they're called), a little white shoe polish is used to determine how far down the sidewall is being used (optimally you want it to almost go to the end of the tread.

Anyone with g-tech or other lateral g meter could find out too, I guess.

For the original poster, I guess they should mess around with rear tire pressures. Either start high (to the sidewall max) and lower them in 2 pound increments (easier) or start low and raise them. I'd put 28 psi at the bottom end.

Every racer I've talked to has told me lower pressure = more grip until you roll over onto the sidewall too much (anything past the tread).

Vaillant

Links for more articles about grip:

On bikes:
http://www.sportrider.com/tech/tires/146_0206_pressure/

On karts:
http://russellkarting.com/settings.htm

On cars:
NSX http://www.nsxprime.com/FAQ/Track/highperfdriving.htm
MGA http://mgaguru.com/mgtech/tires/tt102.htm
Porsche http://www.motormeister.com/suz/ptw_book/ch_11.htm


I've heard different things about different tires. I'm guessing that until someone actually tests these tires on an RX-8 with a pyrometer to actually see at what point are the temperatures even and the full tread being used, we won't know what the best pressure is.

Moral of the story: experiment until you find something you're comforable with.

~ Matt

(edited for typo)

Spin9k

Aside from our air pressure topic, looking to find more info has found (at least for me) a treasure trove of great articles on handling, tuning and more. This is all truly a great read!

I love when what we discuss gets us finding/reading/learning about all manner of other topics related. Thanks Valliant. Great stuffl! :D